Prior to drilling of an oil or gas well bore hole to a desired depth it is necessary to initially drill an entry bore hole and to install surface casing in that bore hole, to protect the surrounding water table, and for other environmental reasons. This must be accomplished before drilling the well to the depth of the earth formation bearing the oil or gas. In this procedure, a tubular conductor pipe is first driven into the earth, and the entry bore hole is drilled after installation of the conductor pipe. Thereafter, it is necessary to remove the drilling equipment and to insert within the drilled entry bore hole, linked tubular metal pipe or well casing which extends from the ground level to the extent of the bore hole and to fixedly locate the well casing in that hole concentric with the conductor pipe. Conventionally, concrete is forced under pressure from the upper end of the well casing after it is inserted in the hole, through the well casing where it flows upwardly between the well casing and the periphery of the bore hole. After solidification of the concrete, the mass of the well casing is fixedly located with respect to that bore hole and drilling procedures to the depth of the oil or gas can proceed. Normally, the level of concrete between the exterior of the well casing and the periphery or wall of the bore hole does not reach the ground level but extends from the bottom of the bore hole vertically upwards for a sufficient distance to maintain the well casing within the earth formation regardless of pressures tending to force it upwardly. While in most cases the concrete is capable of fixing the well casing within the bore hole, there is difficulty in insuring that the well casing is fixed concentric with the conductor pipe, that is, coaxial therewith. Moreover, under conventional procedures, other activities on the drilling platform must await setting of the concrete, and during that time, lateral displacement of the casing can cause accidents and danger to the casing or other equipment. The apparatus of this invention is designed to set in the conductor pipe adjacent ground level in the bottom of an area called the cellar to hang the weight of the surface casings. This results in stabilization of the surface casing relative to the conductor pipe and to adjacent equipment.
The present invention is directed to insuring that the well casing is maintained in proper vertical alignment during setting of the concrete.
It is a further object of the present invention to provide an improved method of fixing a well casing concentrically within its conductor and for maintaining the concentric disposition of the well casing with respect to the bore hole and conductor during solidification of the concrete.